WO2023072486A1

WO2023072486A1 - Ultrasonic sensor for an ultrasonic measuring device, and ultrasonic measuring device

Info

Publication number: WO2023072486A1
Application number: PCT/EP2022/076332
Authority: WO
Inventors: Pierre Ueberschlag
Original assignee: Endress+Hauser Flowtec Ag
Priority date: 2021-10-29
Filing date: 2022-09-22
Publication date: 2023-05-04
Also published as: CN118119828A; DE102021128380A1

Abstract

The invention relates to an ultrasonic sensor (10) for an ultrasonic measuring device (1), comprising: a transducer arrangement (11) for generating and capturing ultrasonic signals with at least one piezo element (11.1), wherein the at least one piezo element is configured, by means of electrodes (11.3), to convert between electrical signals and ultrasonic signals and vice versa; a coupling body (12) for transmitting the ultrasonic signals between a first side surface (12.1) and a second side surface (12.2) of the coupling body, wherein at least one piezo element is arranged on the first side surface, wherein the transducer arrangement has an arrangement amplitude response, characterized in that the arrangement amplitude response is composed of at least two partially overlapping partial amplitude responses (30), wherein different partial amplitude responses that are adjacent in terms of the frequency ranges thereof have a maximum distance, in terms of the central frequencies (32) thereof, from a mean value of the bandwidths thereof multiplied by a factor F, where F is at most 2, and where F is at least 0.2.

Description

Ultrasonic sensor for an ultrasonic measuring device and ultrasonic measuring device

The invention relates to an ultrasonic sensor for an ultrasonic measuring device and such an ultrasonic measuring device for measuring at least one measured variable.

Various designs of ultrasonic sensors are known. For example, sensors are acoustically and mechanically coupled to a wall of a container via coupling bodies in order to radiate ultrasonic signals into the container, see for example DE102017130976A1. It must be taken into account here that the frequency of ultrasonic signals must be matched, for example, to a wall thickness of the wall.

Different sensors are usually kept available for different walls of containers.

The object of the invention is to propose an ultrasonic sensor which can be used flexibly and robustly.

The object is achieved by an ultrasonic sensor according to independent claim 1 and by an ultrasonic measuring device according to independent claim 8.

An ultrasonic sensor according to the invention for an ultrasonic measuring device for measuring at least one measured variable comprises:

A transducer arrangement for generating and detecting ultrasonic signals with at least one piezo element, wherein the at least one piezo element is set up by means of electrodes to convert between electrical signals and ultrasonic signals and vice versa; a coupling body for transmitting the ultrasonic signals between a first side surface and a second side surface of the coupling body, at least one piezo element being arranged on the first side surface, the transducer arrangement having an arrangement amplitude response, wherein the arrangement amplitude response is composed of at least two partially overlapping partial amplitude responses, which partial amplitude responses each have a bandwidth measured by a half-value width and a central frequency, wherein different partial amplitude responses that are adjacent in terms of their frequency ranges have a maximum distance from a mean value of their bandwidths multiplied by a factor F with regard to their central frequencies, where F is at most 2, and where F is in particular at most 1.5, and where F is preferably at most 1, and where F is at least 0.2, and where F is in particular at least 0.4, and where F is preferably at least 0.5.

An amplitude response describes a frequency-dependent relationship between amplitudes of an electrical signal and amplitudes of an ultrasonic signal and thus provides an indication of a range of use of a transducer arrangement. In this case, large values of an amplitude response correspond to good conversion efficiency between electrical signals and ultrasonic signals.

A usable frequency range of an ultrasonic sensor can be expanded by the overlapping of several partial amplitude responses in an arrangement amplitude response. In this way, the ultrasonic sensor can be used flexibly and robustly with different containers. A user can thus select an ultrasonic signal suitable for a wall of a container, such as a measuring tube, for many applications, without reaching an application limit of the ultrasonic sensor and having to change it. For this purpose, the sensor is coupled acoustically and mechanically to the container via its second side surface.

By means of the electrodes, the piezo effect can be utilized when an electrical voltage that varies over time is applied in order to excite the associated piezo element to oscillate. In this way, ultrasonic signals can be generated. Conversely, externally imposed vibrations lead to the

ADJUSTED SHEET (RULE 91) ISA/EP Piezo element internal electrical voltages generated, which can be tapped through the electrodes as a measurement signal. In this way, ultrasonic signals can be detected.

In one configuration, the transducer arrangement has at least two piezo elements, with at least two piezo elements of the at least two piezo elements each having a different piezo amplitude response. In this way, the planning and production of the transducer arrangement can be simplified.

In one embodiment, piezo elements with different piezo amplitude response are arranged coaxially to one another.

In this way, the signal path profiles of ultrasonic signals generated by piezo elements with different amplitude responses are the same.

In one configuration, a first piezo element is disc-shaped, with at least one second piezo element being ring-shaped, with the at least one second piezo element having a ring area and a free central area, with the first piezo element being arranged in the central area of the at least one second piezo element, or with the second Piezo element is mounted on the first piezo element, wherein the first piezo element is arranged on the first side surface of the coupling body.

In this way, a coaxial arrangement of different piezo elements can be achieved.

In one embodiment, piezo elements with different piezo amplitude response have different thicknesses.

A resonant frequency of a piezo element is essentially determined by its geometric dimensions and in particular by its thickness.

In one embodiment, a piezo element has a piezo amplitude response

ADJUSTED SHEET (RULE 91) ISA/EP which piezo amplitude response is composed of at least two overlapping partial amplitude responses, which partial amplitude responses each have a bandwidth measured by a half-value width and a central frequency, wherein different adjacent partial amplitude responses with regard to their central frequencies have a maximum distance from a mean value of their bandwidths multiplied by a factor F, with F at most 2, and where F is in particular at most 1, where the piezo element is disk-shaped and has a first thickness in sections, and where the piezo element has a second thickness in sections, with a side surface of the piezo element being flat and being acoustically coupled to the first side surface of the coupling body.

In this way, an adjustment of several piezo elements to each other can be avoided.

In one embodiment, the piezo element has a depression in a central area.

An ultrasonic measuring device according to the invention for measuring at least one measured variable comprises:

At least one ultrasonic sensor according to one of the preceding claims, an electronic measuring/operating circuit for operating the at least one ultrasonic sensor and for providing measured values of the at least one measured variable.

The invention is described below using exemplary embodiments.

figs 1 a) and b) show an exemplary ultrasonic sensor according to the invention from different views;

figs 2 a) to c) show exemplary converter arrangements according to the invention;

ADJUSTED SHEET (RULE 91) ISA/EP 3 shows exemplary partial amplitude responses;

figs 4 a) and b) show exemplary ultrasonic measuring devices.

1 a) shows a side view of an exemplary ultrasonic sensor 10 according to the invention with a transducer arrangement 11 which is arranged on a first side surface 12.1 of a coupling body 12 and is acoustically coupled to it. According to the invention, the transducer arrangement 11 has an arrangement amplitude response which is composed of at least two overlapping partial amplitude responses, see Figs. 2 a) to c) and Fig. 3 b). An arrangement amplitude response describes a frequency-dependent relationship between amplitudes of an electrical signal and amplitudes of an ultrasonic signal and thus gives an indication of a range of use of a transducer arrangement. In this case, large values of the arrangement amplitude response correspond to good conversion efficiency between electrical signals and ultrasonic signals.

The coupling body has a second side face 12.2, which is designed to connect with a wall 40.1 of a container 40, see Figs. 4 a) and 4 b) to be acoustically coupled. The container can be, for example, a measuring tube or a tank, for example for a fluid such as a liquid.

Fig. 1 b) shows an oblique view of the ultrasonic sensor shown in Fig. 1 a), with the transducer arrangement 11 having, by way of example, a disc-shaped first piezo element 11.1 and a ring-shaped second piezo element 11.2 with a ring area 11.121, with the first piezo element being arranged coaxially in a central area 11 .122 of the second piezo element is arranged, the two piezo elements having different arrangement amplitude responses.

figs 2 a), b) and c) outline exemplary transducer arrangements 11 according to the invention, by means of which an arrangement amplitude response according to the invention can be set up. The examples shown here are not to be interpreted as limiting.

Fig. 2 a) shows a cross section through a transducer arrangement as shown in Fig. 1 b), wherein a disc-shaped first piezoelectric element 11.11 in a

ADJUSTED SHEET (RULE 91) ISA/EP Central area of an annular second piezoelectric element is arranged 11.12. A resonant frequency of a piezo element is essentially determined by its geometric dimensions and in particular by its thickness. The thicker a piezo element, the lower its resonant frequency. As shown here, for example, the second piezo element 11.12 can have a greater thickness than the central first piezo element, so that the second piezo element has a lower resonant frequency. This can be achieved, for example, in that an arrangement amplitude response of the transducer arrangement 11 is composed of different, overlapping amplitude responses, which amplitude responses each belong to a piezo element. Both piezo elements are acoustically and mechanically coupled to the coupling body 12 . By means of electrodes 11.3, the piezoelectric elements can be excited to oscillate and externally applied oscillations can be detected.

For example, the arrangement amplitude response can be expanded by further ring-shaped piezo elements, which are arranged concentrically around the second piezo element 11.12 shown here. For example, the disc-shaped first piezo element shown here can alternatively also be ring-shaped.

Since an ultrasonic emission characteristic is characterized by a ratio of the wavelength of an ultrasonic signal to the diameter of a corresponding piezo element, emission characteristics of different piezo elements in a transducer arrangement can be matched to one another as a side effect.

2b) shows an alternative transducer arrangement according to the invention, with the ring-shaped second piezo element 11.12 being mounted on the disc-shaped first piezo element 11.11. Here the first piezoelectric element 11.11 is in contact with the coupling body 12. As in FIG. 2a), both piezoelectric elements have different thicknesses, so that an arrangement amplitude response of the transducer arrangement is composed of different, overlapping partial amplitude responses. The piezo elements also have electrodes 11.3 in order to generate and detect vibrations.

Fig. 2c) shows a further embodiment according to the invention, in which a first piezoelectric element 11.1 is designed in the form of a disk and in a central area a

ADJUSTED SHEET (RULE 91) ISA/EP has taper. Due to the exemplary arrangement of the electrodes 11.3 shown here in combination with the geometric design, the first piezoelectric element has a piezoelectric amplitude response made up of different, overlapping partial amplitude responses, which each belong to different pairs of electrodes.

3 outlines exemplary, schematic partial amplitude responses 30, for example, of two piezo elements, with the vertical axis representing a frequency-dependent amplitude and the horizontal axis representing an excitation frequency, for example. The solid frequency spectrum is slightly lower in frequency than the dashed frequency spectrum. Both partial amplitude responses each have a half-value width 31 and each have a central frequency 32 and overlap. As shown here, the partial amplitude responses can be similar or different. In practice, such partial amplitude responses are significantly less smooth, FIG. 3 is for illustrative purposes only.

According to the invention, different partial amplitude responses that are adjacent in terms of their frequency ranges have a maximum distance from a mean value of their bandwidths with regard to their central frequencies multiplied by a factor F, where F is at most 2, and where F is in particular at most 1.5, and where F is preferably at most 1, and where F is at least 0.2 , and where F is especially at least 0.4, and where F is especially at least 0.5.

A maximum distance is defined by an upper limit of F, and a minimum distance by a lower limit of F. In this way, an uninterrupted array amplitude response is constructed using just a few different piezo elements.

The solid partial amplitude response here belongs to a piezo element with a greater thickness (Figs. 2 a), b) or to a pair of electrodes with a larger spacing (Fig. 2 c)), the broken partial amplitude response corresponds to a piezo element with a smaller thickness (Figs 2 a), b) or to a pair of electrodes with a smaller distance (Fig. 2 c)).

In the case of the 2 a) to c) shown transducer arrays is an associated array amplitude response expanded, so that in a larger frequency range

ADJUSTED SHEET (RULE 91) ISA/EP than with conventional transducer arrangements, ultrasonic signals can be efficiently generated and detected. Depending on how the piezo elements are connected to form a transducer arrangement, an arrangement amplitude response of a transducer arrangement according to the invention is thus composed, for example, essentially of partial amplitude responses of individual piezo elements or corresponds to their sum.

For example, a single piezo element can have a piezo amplitude response, which piezo amplitude response is composed of at least two overlapping partial amplitude responses 30 , which partial amplitude responses each have a bandwidth 31 measured by a half-value width and a central frequency 32 . This can be implemented, for example, by means of a piezo element according to FIG. 2c).

According to the invention, different partial amplitude responses that are adjacent in terms of their frequency ranges have a maximum distance from a mean value of their bandwidths with regard to their central frequencies 32 multiplied by a factor F, where F is at most 2, and where F is in particular at most 1. In this way it is ensured that a transducer arrangement in a coherent frequency range and not in several separate frequency ranges.

figs 4 a) and b) outline exemplary ultrasonic measuring devices 1 with at least one ultrasonic sensor 10 according to the invention and an electronic measuring/operating circuit 20 for operating the at least one ultrasonic sensor and for providing measured values of at least one measured variable. The at least one ultrasonic sensor 10 is attached to an outside of a wall 40.1 of a container 40 and is set up to radiate ultrasonic signals into the container and to receive ultrasonic signals emerging from the container.

Fig. 4 a) outlines an exemplary ultrasonic flow meter 1.1 after

Transit time difference measurement principle, with a transit time difference of

Ultrasonic signals between two ultrasonic sensors according to the invention 10 in

ADJUSTED SHEET (RULE 91) ISA/EP and against the direction of flow of a medium flowing through a measuring tube 41 is used to determine a flow rate.

Fig. 4b) outlines an ultrasonic fill level measuring device 1.2, in which a fill level of a medium in a tank 42 is measured over an ultrasonic signal propagation time from an ultrasonic signal emitted by the ultrasonic sensor 10, partially reflected at an interface of the medium and received again.

In order for ultrasonic signals to be able to penetrate well through a wall of a container, an ultrasonic signal spectrum must be matched to the wall. Transducer arrangements according to the invention are capable of generating and detecting ultrasonic signals in a wide frequency range, so that a user does not have to change the ultrasonic sensors when changing a container 40 . In this way, an ultrasonic measuring device according to the invention can be used in a variety of ways and costs can therefore be saved.

ADJUSTED SHEET (RULE 91) ISA/EP Reference List

1 ultrasonic measuring device

1.1 Ultrasonic flow meter

I .2 Ultrasonic Level Gauge

10 ultrasonic sensor

11 transducer assembly

I I .1 piezo element

11.101 side face

11.102 Central Area

11.11 first piezo element

11.12 second piezo element

11.121 ring area

11.122 Central Area

11.3 Electrode

12 coupling bodies

12.1 first face

12.2 second face

20 electronic measurement/operation circuit

30 partial amplitude response

31 bandwidth

32 center frequency

40 container wall

measuring tube

tank

Claims

patent claims

1. Ultrasonic sensor (10) for an ultrasonic measuring device (1) comprising:

A transducer arrangement (11) for generating and detecting ultrasonic signals with at least one piezo element (11.1), wherein the at least one piezo element is set up by means of electrodes (11.3) to convert between electrical signals and ultrasonic signals and vice versa; a coupling body (12) for transmitting the ultrasonic signals between a first side surface (12.1) and a second side surface (12.2) of the coupling body, at least one piezo element being arranged on the first side surface, the transducer arrangement having an arrangement amplitude response, characterized in that the arrangement amplitude response is composed of at least two partially overlapping partial amplitude responses (30), which partial amplitude responses each have a bandwidth (31) measured by a half-value width and a central frequency (32), wherein different partial amplitude responses that are adjacent in terms of their frequency ranges have a maximum distance of one in terms of their central frequencies (32). Average of their bandwidths multiplied by a factor F, where F is at most 2, and where F is in particular at most 1.5, and where F is preferably at most 1, and where F is at least 0.2, and where F is in particular at least 0.4, and where F is preferably at least 0.5 .

2. Ultrasonic sensor according to claim 1, wherein the transducer arrangement (11) has at least two piezo elements (11.1), wherein at least two piezo elements of the at least two piezo elements each have a different piezo amplitude response.

3. Ultrasonic sensor according to claim 2, wherein piezo elements (11.1) with different piezo amplitude response are arranged coaxially to each other.

4. Ultrasonic sensor according to claim 3, wherein a first piezo element (11.11) of the piezo elements with a different amplitude response is disc-shaped or ring-shaped, and wherein at least a second piezo element (11.12) of the piezo elements with a different amplitude response is ring-shaped, the at least one second piezo element having a ring area (11.121) and a free central area (11.122), the first piezo element being arranged in the central area of the at least one second piezo element, or the second piezo element being mounted on the first piezo element, the first piezo element being on the first side surface of the coupling body is arranged.

5. Ultrasonic sensor according to one of the preceding claims, wherein piezo elements (11.1) with different piezo amplitude response have different thicknesses.

6. Ultrasonic sensor according to one of the preceding claims, wherein at least one piezo element (11.1) has a piezo amplitude response, which piezo amplitude response is composed of at least two partially overlapping partial amplitude responses (30), which partial amplitude responses each have a bandwidth (31) measured by a half-value width and a central frequency ( 32), wherein different adjacent frequency ranges with regard to their central frequencies (32) have a maximum distance from a mean value of their bandwidths multiplied by a factor F, with F at most 2, and with F in particular at most 1, the piezo element being disk-shaped and having a first thickness in sections has, and wherein the piezo element has a second thickness in sections, 14 wherein a side surface (11.101) of the piezo element is flat and is acoustically coupled to the first side surface of the coupling body.

7. Ultrasonic sensor according to claim 6, wherein the piezo element (11 .1) in a central region (11 .102) has a depression.

8. Ultrasonic measuring device (1) for measuring at least one measurand, comprising:

At least one ultrasonic sensor (10) according to one of the preceding claims, an electronic measuring/operating circuit (20) for operating the at least one ultrasonic sensor and for providing measured values of the at least one measured variable.